UNLABELLED: In recent years substantial progress has been seen in the development of approaches and methods for serological diagnosis of the mycosis. The aim of our study was to assess the clinical usefulness of serological tests for fungal infection in pts who underwent prolonged antibiotic therapy after valve replacement. MATERIAL AND METHODS: The group consisted of 27 pts after valve replacement with prolonged antibiotic therapy (6-12 weeks) due to infective endocarditis (22 pts) or sternal infection (5 pts). The samples of blood were taken 10 days after antibiotics were started and next every 10 days. Serological techniques for the diagnosis of Candidiasis consisted of antibody detection to: the cell wall polysaccharide antigen (test A), cytoplasmic protein antigen (test B) and the germ tube antigens (test C). RESULTS: Patients were divided in 3 groups due to the kinetics of the antibody responses to the Candida antigen: 1. pts with normal level of antibody during antibiotic treatment--they didn't required antifungal therapy, 2. pts with increasing level of antibody needed antifungal treatment, 3. pts with increasing kinetics of antibody responses during antibiotic and antifungal treatment needed the change of antifungal therapy, 4. Control group (pts before cardiac surgery without any sign of fungal infection). Antibody to the cytoplasmic antigen was detected infrequently. The presence of antibody to the cytoplasmic antigen was correlated with the patient clinical outcome and prognosis and necessity for change of antifungal therapy. One pt died after valve replacement due to valve dysfunction because of fungal endocarditis. CONCLUSIONS: Serological tests for Candidiasis can be a useful marker of fungal infection, prognosis and treatment in pts required prolonged antibiotic therapy after valve replacement.